The purpose of this longitudinal study was to explore the development of pre-service chemistry teachers' pedagogical content knowledge regarding the effect of temperature on reaction rate topic as they took pedagogical content knowledge courses throughout the teacher education program. Pre-service teachers' pedagogical content knowledge was examined under five components: Orientations toward science teaching, Knowledge of curriculum, Knowledge of instructional strategies, Knowledge of learners, and Knowledge of assessment. Two pre-service chemistry teachers participated in the study. Data were collected through a vignette and semi-structured interviews over two years. Analysis of data revealed that both participants' pedagogical content knowledge components showed development. However, there was an uneven development of components of pedagogical content knowledge. Moreover, the degree and pattern of development were different for some components of pedagogical content knowledge for each participant. The present study has some implications for teacher educators and teacher education programs.